The invention relates to a lens, to an instrument for inserting an intraocular lens into an eye, to a method for preparing an intraocular lens for insertion into an eye and to a method for inserting an intraocular lens into an eye, including such a preparatory method. Such a lens, such an instrument and such methods are known from U.S. Pat. No. 4,573,998.
Implantation of an intraocular lens after surgical removal of the opaque lens, a structure having a thickness of about 5 millimeters and diameter of about 9 millimeters, from the eye of a cataract patient is one of the most common forms of eye surgery. The lens is usually implanted in the anterior chamber of the eye (in front of the iris) or in the posterior chamber of the eye (behind the iris) in the capsular bag or in the sulcus.
Another indication for the prescription of intraocular lenses is optical correction of the natural lens. For that purpose the lens is implanted in the anterior chamber of the eye, in front of the natural lens in its natural position. An example of such a lens is disclosed in U.S. Pat. No. 5,192,319. This lens has a rigid optical portion and, disposed along the circumference of the optical portion, haptics in the form of pairs of arms which are flexible but stiff enough to pinch a plea of iris material between free ends thereof for retaining the lens relative to the iris.
The implantation of an intraocular lens involves making a corneal or corneoscleral incision. The intraocular lens is inserted through this incision into the eye. It has long been recognized that it is advantageous if the lens to be implanted can be passed through a small incision, in particular if the natural lens is not removed or if the natural lens is removed after having been emulsified, so that the size of the incision does not have to meet requirements originating from the need to remove the natural lens through that incision. A disadvantage of the rigid intraocular lens is that insertion of the lens requires a relatively large incision in the ocular tissue.
Another option described in this document is to insert the deformable lens via a channel with a circular cross-section. The lens is released from the channel behind the incision. Release of the lens and the position of the lens before insertion in the tube and after release from the tube are difficult to control.
In U.S. Pat. No. 5,047,051, it is proposed to mount the deformable optical portion of the lens to a semi-rigid haptic anchor plate surrounding the deformable optical portion to which anchor plate relatively short looped haptics are attached. However, the semi-rigid anchor plate reduces compressibility of the lens and unfolding of the semi-rigid plate in the anterior chamber of the eye entails a risk of damaging eye tissue bounding the anterior chamber and in particular the cornea.
In U.S. Pat. No. 5,147,395, it is proposed to provide a lens with a fixation member including a deformable element integral with the deformable optic and at least one resilient stiffening element within the deformable element and the optic. This entails that the stiffening element extends within the optic and accordingly reduces the effective optical area of the lens.
In U.S. Pat. No. 5,562,676, it is mentioned to push, pull or carry a lens through a lumen projecting into an eye, for inserting the lens into an eye. For pulling or carrying the lens through the lumen, the use of a forceps is mentioned, which forceps enters the lumen proximally. This entails that the forceps, which needs to extend in the lumen along the lens, occupies a relatively large portion of the cross-section of the lumen in the section of the lumen where the lens is located. Moreover, reliable engagement of the forceps extending through a narrow lumen is difficult to ensure. The lens has relatively slender haptics which can easily be damaged during passage through the lumen.
In international patent application publ. no. WO 95/21594, it is described to suck a lens having a deformable optic into a tube having an internal diameter of 4 mm using a loading funnel. After the distal end of the tube is inserted into the eye, the lens is ejected from the tube by applying pressure to fluid behind the lens. The emergence of the lens from the tube is difficult to control, in particular with respect to the velocity with which the lens regains its original shape and the orientation of the lens after emergence from the tube.
In European patent application 0,766,952 a lens is proposed of which the haptics and the optical part are of shape-recovery materials, the material of the haptics recovering shape more quickly than the material of the lens. Shape recovery is obtained by hydration or temperature. This requires stringent control of the humidity or temperature of the lens before insertion. Furthermore, preparation of the lenses requires hydration or heating, deformation, and drying or cooling in deformed condition, which is relatively cumbersome.
In U.S. Pat. No. 5,843,187, it is described to reduce the transverse dimensions of an intraocular lens during passage through an incision in the eye by stretching the lens in the direction of insertion. To achieve this, holes in the haptics are engaged by micro hooks. Disadvantages of this treatment are that engaging the lens with the micro hooks is cumbersome and that a further incision in the eye is made for insertion of the second micro hook instrument that pulls the lens into the eye. Furthermore, coordinated control of the two instruments inserted into the eye via different incisions is relatively difficult.